Waveguides are used to guide electrical fields. An orthomode transducer (OMT) is a type of waveguide which is designed to decompose an arbitrarily polaried electrical field into its various components. Prior art OMT's are typically of tubular construction, with one of the feed ports located on the cylindrical sidewall and the other feed port located on the circular endwall. Alternatively, the OMT may have a square or rectangular cross section with a corresponding square or rectangular endwall.
On prior art OMT's, the signal used to feed the endwall port must pass over the septum used to feed the sidewall port, thus causing interference. The length of the septum is resonant at some frequency, which decreases the usable band width of the endwall feed port. Moreover, the endwall port increases the overall length of the OMT, and thus coupling two OMT's together is made more difficult, as side mounted phase shifters must be employed.